U.S. patent application number 11/339776 was filed with the patent office on 2006-09-21 for control device for internal combustion engine.
This patent application is currently assigned to Toyota Jidosha Kabushiki Kaisha. Invention is credited to Yukikazu Ito, Kenichi Kinose.
Application Number | 20060207557 11/339776 |
Document ID | / |
Family ID | 36643399 |
Filed Date | 2006-09-21 |
United States Patent
Application |
20060207557 |
Kind Code |
A1 |
Ito; Yukikazu ; et
al. |
September 21, 2006 |
Control device for internal combustion engine
Abstract
An engine ECU executes a program including the steps of:
starting an engine by transiently increasing an amount of fuel
injection when a start request is detected; prohibiting calculation
of a learn value when a condition for stopping transient increase
is not satisfied; stopping transient increase when the condition
for stopping transient increase is satisfied; steadily increasing
the amount of fuel injection in accordance with a coolant
temperature TW; and permitting calculation of a learn value during
steady increase in accordance with the coolant temperature TW.
Inventors: |
Ito; Yukikazu;
(Nishikamo-gun, JP) ; Kinose; Kenichi;
(Okazaki-shi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
Toyota Jidosha Kabushiki
Kaisha
Toyota-shi
JP
|
Family ID: |
36643399 |
Appl. No.: |
11/339776 |
Filed: |
January 26, 2006 |
Current U.S.
Class: |
123/431 |
Current CPC
Class: |
F02D 41/068 20130101;
F02D 41/2454 20130101; F02D 41/2445 20130101; F02D 41/062 20130101;
F02D 41/2448 20130101; F02D 41/3094 20130101 |
Class at
Publication: |
123/431 |
International
Class: |
F02B 7/00 20060101
F02B007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 18, 2005 |
JP |
2005-078292 |
Claims
1. A control device for an internal combustion engine, said
internal combustion engine including a first fuel injection
mechanism injecting fuel into a cylinder and a second fuel
injection mechanism injecting fuel into an intake manifold,
comprising: a first control unit controlling said fuel injection
mechanism so that the fuel is injected solely from any one of said
first fuel injection mechanism and said second fuel injection
mechanism at least during cranking and idling in which a
temperature of said internal combustion engine is equal to or lower
than a predetermined value; a second control unit controlling said
fuel injection mechanism so that the fuel is injected from said
first fuel injection mechanism and said second fuel injection
mechanism; a calculation unit calculating a correction value for an
amount of fuel injection based on an air-fuel ratio; a prohibition
unit prohibiting calculation of a correction value for an amount of
fuel injection at least during a period from start of cranking of
said internal combustion engine to full combustion thereof; and a
permission unit permitting calculation of a correction value for an
amount of fuel injection during a predetermined period after full
combustion of said internal combustion engine.
2. The control device for an internal combustion engine according
to claim 1, wherein said first control unit controls said fuel
injection mechanism so that the fuel is injected solely from said
second fuel injection mechanism during cranking and idling in which
the temperature of said internal combustion engine is equal to or
lower than the predetermined value.
3. The control device for an internal combustion engine according
to claim 1, wherein said predetermined period is a period during
which the amount of fuel injection is corrected based on the
temperature of said internal combustion engine.
4. The control device for an internal combustion engine according
to claim 3, further comprising a correction prohibition unit
prohibiting correction of the amount of fuel injection based on the
correction value calculated when the amount of fuel injection is
corrected based on a factor other than the temperature and the
air-fuel ratio of said internal combustion engine.
5. The control device for an internal combustion engine according
to claim 1, wherein said first fuel injection mechanism is an
in-cylinder injector, and said second fuel injection mechanism is
an intake manifold injector.
6. A control device for an internal combustion engine, said
internal combustion engine including first fuel injection means
injecting fuel into a cylinder and second fuel injection means
injecting fuel into an intake manifold, comprising: first control
means for controlling said fuel injection means so that the fuel is
injected solely from any one of said first fuel injection means and
said second fuel injection means at least during cranking and
idling in which a temperature of said internal combustion engine is
equal to or lower than a predetermined value; second control means
for controlling said fuel injection means so that the fuel is
injected from said first fuel injection means and said second fuel
injection means; calculation means for calculating a correction
value for an amount of fuel injection based on an air-fuel ratio;
prohibition means for prohibiting calculation of a correction value
for an amount of fuel injection at least during a period from start
of cranking of said internal combustion engine to full combustion
thereof; and permission means for permitting calculation of a
correction value for an amount of fuel injection during a
predetermined period after full combustion of said internal
combustion engine.
7. The control device for an internal combustion engine according
to claim 6, wherein said first control means includes means for
controlling said fuel injection means so that the fuel is injected
solely from said second fuel injection means during cranking and
idling in which the temperature of said internal combustion engine
is equal to or lower than the predetermined value.
8. The control device for an internal combustion engine according
to claim 6, wherein said predetermined period is a period during
which the amount of fuel injection is corrected based on the
temperature of said internal combustion engine.
9. The control device for an internal combustion engine according
to claim 8, further comprising means for prohibiting correction of
the amount of fuel injection based on the correction value
calculated when the amount of fuel injection is corrected based on
a factor other than the temperature and the air-fuel ratio of said
internal combustion engine.
10. The control device for an internal combustion engine according
to claim 6, wherein said first fuel injection means is an
in-cylinder injector, and said second fuel injection means is an
intake manifold injector.
11. The control device for an internal combustion engine according
to claim 2, wherein said first fuel injection mechanism is an
in-cylinder injector, and said second fuel injection mechanism is
an intake manifold injector.
12. The control device for an internal combustion engine according
to claim 3, wherein said first fuel injection mechanism is an
in-cylinder injector, and said second fuel injection mechanism is
an intake manifold injector.
13. The control device for an internal combustion engine according
to claim 4, wherein said first fuel injection mechanism is an
in-cylinder injector, and said second fuel injection mechanism is
an intake manifold injector.
14. The control device for an internal combustion engine according
to claims 7, wherein said first fuel injection means is an
in-cylinder injector, and said second fuel injection means is an
intake manifold injector.
15. The control device for an internal combustion engine according
to claims 8, wherein said first fuel injection means is an
in-cylinder injector, and said second fuel injection means is an
intake manifold injector.
16. The control device for an internal combustion engine according
to claims 9, wherein said first fuel injection means is an
in-cylinder injector, and said second fuel injection means is an
intake manifold injector.
Description
[0001] This nonprovisional application is based on Japanese Patent
Application No. 2005-078292 filed with the Japan Patent Office on
Mar. 18, 2005, the entire contents of which are hereby incorporated
by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a control device for an
internal combustion engine that includes a first fuel injection
mechanism (in-cylinder injector) injecting fuel into a cylinder and
a second fuel injection mechanism (intake manifold injector)
injecting fuel into an intake manifold or an intake port, and more
particularly to a technique to correct an amount of fuel injection
from the first fuel injection mechanism and the second fuel
injection mechanism.
[0004] 2. Description of the Background Art
[0005] An internal combustion engine provided with an intake
manifold injector for injecting fuel into an intake manifold and an
in-cylinder injector for constantly injecting fuel into a
combustion chamber, in which fuel injection from the intake
manifold injector is stopped when load of the engine is lower than
preset load and fuel injection from the intake manifold injector is
allowed when load of the engine is higher than the preset load, is
known.
[0006] Even in such an internal combustion engine, a desired amount
of fuel injection may not be attained due to deposits accumulated
in the injector or difference between individual engines caused
during manufacturing. Namely, an air-fuel ratio may deviate from a
desired air-fuel ratio (for example, stoichiometric air-fuel
ratio). In order to correct such deviation in the amount of fuel
injection, the amount of fuel injection is corrected by feedback
control of the air-fuel ratio, as in an internal combustion engine
including one injector for each cylinder.
[0007] Japanese Patent Laying-Open No. 03-185242 discloses a fuel
injection amount control device for an internal combustion engine
that accurately corrects an amount of fuel injection in the
internal combustion engine including a plurality of fuel injection
valves for each cylinder. The fuel injection amount control device
includes a control unit controlling fuel injection from the
plurality of fuel injection valves in accordance with an operation
state, a learning unit learning a value based on an output signal
from an oxygen sensor provided in an exhaust system of the engine
so as to correct the amount of fuel injection, a setting unit
setting a plurality of learning regions corresponding to states of
use of the plurality of fuel injection valves, and a correction
unit using each learn value learned in the learning region to
correct the amount of fuel injection in the operation state
corresponding to each learning region.
[0008] According to the fuel injection amount control device
described in this publication, as the fuel injection valve used in
the learning region is the same as that used in correcting the
amount of fuel injection with the learn value, accuracy in
correcting the amount of fuel injection is improved. Therefore,
follow-up characteristic of the air-fuel ratio is enhanced and
exhaust emission is improved. In addition, as deviation from a
target air-fuel ratio becomes small, possibility of misfire is
suppressed and fuel efficiency can be improved even if a leaner
air-fuel ratio is set.
[0009] Meanwhile, in the internal combustion engine, for example at
the time of cold start, the amount of fuel injection may be
increased in order to improve starting capability. When the amount
of fuel injection is increased like this, the air-fuel ratio may
necessarily vary, as compared with a case in which the amount of
fuel injection is not increased. The fuel injection amount control
device according to Japanese Patent Laying-Open No. 03-185242,
however, does not take into consideration such a case in which the
amount of fuel injection is increased. Therefore, the amount of
fuel injection may unnecessarily be corrected as a result of
learning of the learn value, and correction of the amount of fuel
injection based on the learn value may be inappropriate.
SUMMARY OF THE INVENTION
[0010] An object of the present invention is to provide a control
device for an internal combustion engine capable of appropriately
correcting an amount of fuel injection.
[0011] A control device for an internal combustion engine according
to the present invention controls an internal combustion engine
including a first fuel injection mechanism injecting fuel into a
cylinder and a second fuel injection mechanism injecting fuel into
an intake manifold. The control device includes: a first control
unit controlling the fuel injection mechanism so that the fuel is
injected solely from any one of the first fuel injection mechanism
and the second fuel injection mechanism at least during cranking
and idling in which a temperature of the internal combustion engine
is equal to or lower than a predetermined value; a second control
unit controlling the fuel injection mechanism so that the fuel is
injected from the first fuel injection mechanism and the second
fuel injection mechanism; a calculation unit calculating a
correction value for an amount of fuel injection based on an
air-fuel ratio; a prohibition unit prohibiting calculation of a
correction value for an amount of fuel injection at least during a
period from start of cranking of the internal combustion engine to
full combustion thereof; and a permission unit permitting
calculation of a correction value for an amount of fuel injection
during a predetermined period after full combustion of the internal
combustion engine.
[0012] According to the present invention, the first control unit
controls the fuel injection mechanism so that the fuel is injected
solely from any one of the first fuel injection mechanism and the
second fuel injection mechanism at least during cranking and idling
in which the temperature of the internal combustion engine is equal
to or lower than the predetermined value. The second control unit
controls the fuel injection mechanism so that the fuel is injected
from the first fuel injection mechanism and the second fuel
injection mechanism. In the internal combustion engine in which the
fuel injection mechanism is controlled in such a manner, it is not
always the case that there are many occasions in which the fuel is
injected solely from any one of the first fuel injection mechanism
and the second fuel injection mechanism. Accordingly, it is not
always the case that there are many occasions to calculate the
correction value for the amount of fuel injection while the fuel is
injected solely from any one of the first fuel injection mechanism
and the second fuel injection mechanism. Therefore, in a state in
which the fuel is injected solely from any one of the first fuel
injection mechanism and the second fuel injection mechanism, the
correction value for the amount of fuel injection should be
calculated as many times as possible. Hence, the correction value
may be calculated also during a cold state of the internal
combustion engine in which the fuel may be injected solely from any
one of the first fuel injection mechanism and the second fuel
injection mechanism (including cranking and idling in which the
temperature of the internal combustion engine is not higher than
the predetermined value). At the time of start in the cold state of
the internal combustion engine, at least during a period from the
start of cranking to full combustion, the amount of fuel injection
may transiently be corrected (increased). Meanwhile, during a
predetermined period after full combustion, the amount of fuel
injection may steadily be corrected (increased) in accordance with
the temperature of the internal combustion engine. While the
injection amount is transiently increased, the air-fuel ratio may
suddenly change. On the other hand, while the injection amount is
steadily increased, the air-fuel ratio is stable. Accordingly, at
least during the period from the start of cranking to full
combustion, calculation of the correction value for the amount of
fuel injection is prohibited, and during the predetermined period
after full combustion, calculation of the correction value for the
amount of fuel injection is permitted. Therefore, the correction
value for the amount of fuel injection can be calculated while the
air-fuel ratio is stable, and miscalculation of the correction
value can be suppressed. Consequently, a control device for an
internal combustion engine capable of appropriately correcting an
amount of fuel injection can be provided.
[0013] Preferably, the first control unit controls the fuel
injection mechanism so that the fuel is injected solely from the
second fuel injection mechanism during cranking and idling in which
the temperature of the internal combustion engine is equal to or
lower than the predetermined value.
[0014] According to the present invention, the fuel injection
mechanism is controlled so that the fuel is injected solely from
the second fuel injection mechanism during cranking and idling in
which the temperature of the internal combustion engine is equal to
or lower than the predetermined value. In the internal combustion
engine in which the fuel injection mechanism is controlled in such
a manner, it is not always the case that there are many occasions
in which the fuel is injected solely from the second fuel injection
mechanism. Accordingly, it is not always the case that there are
many occasions to calculate the correction value for the amount of
fuel injection while the fuel is injected solely from the second
fuel injection mechanism. Therefore, in a state in which the fuel
is injected solely from the second fuel injection mechanism, the
correction value for the amount of fuel injection should be
calculated as many times as possible. Hence, the correction value
may be calculated also during a cold state of the internal
combustion engine in which the fuel may be injected solely from the
second fuel injection mechanism (including cranking and idling in
which the temperature of the internal combustion engine is not
higher than the predetermined value). At the time of start in the
cold state of the internal combustion engine, at least during a
period from the start of cranking to full combustion, the amount of
fuel injection may transiently be corrected (increased). Meanwhile,
during a predetermined period after full combustion, the amount of
fuel injection may steadily be corrected (increased) in accordance
with the temperature of the internal combustion engine. While the
injection amount is transiently increased, the air-fuel ratio may
suddenly change. On the other hand, while the injection amount is
steadily increased, the air-fuel ratio is stable. Accordingly, at
least during the period from the start of cranking to full
combustion, calculation of the correction value for the amount of
fuel injection is prohibited, and during the predetermined period
after full combustion, calculation of the correction value for the
amount of fuel injection is permitted. Therefore, the correction
value for the amount of fuel injection can be calculated while the
air-fuel ratio is stable, and miscalculation of the correction
value can be suppressed.
[0015] Preferably, the predetermined period is a period during
which the amount of fuel injection is corrected based on the
temperature of the internal combustion engine.
[0016] According to the present invention, the air-fuel ratio is
stable while the amount of fuel injection is steadily corrected in
accordance with the temperature of the internal combustion engine.
During such a period, calculation of the correction value for the
amount of fuel injection is permitted. Therefore, the correction
value for the amount of fuel injection can be calculated while the
air-fuel ratio is stable, and miscalculation of the correction
value can be suppressed.
[0017] Preferably, the control device further includes a correction
prohibition unit prohibiting correction of the amount of fuel
injection based on the correction value calculated when the amount
of fuel injection is corrected based on a factor other than the
temperature and the air-fuel ratio of the internal combustion
engine.
[0018] According to the present invention, correction of the amount
of fuel injection based on the correction value calculated when the
amount of fuel injection is corrected based on a factor other than
the temperature and the air-fuel ratio of the internal combustion
engine (such as fuel adhered to a wall surface of an intake port or
fuel purged from a canister) is prohibited. Accordingly,
unnecessary correction of the amount of fuel injection with the
correction value calculated when the amount of fuel injection is
transiently corrected based on the fuel adhered to the wall surface
of the intake port or the fuel purged from the canister can be
suppressed. Therefore, the amount of fuel injection can
appropriately be corrected.
[0019] Preferably, the first fuel injection mechanism is an
in-cylinder injector, and the second fuel injection mechanism is an
intake manifold injector.
[0020] According to the present invention, in the internal
combustion engine in which the in-cylinder injector serving as the
first fuel injection mechanism and the intake manifold injector
serving as the second fuel injection mechanism are separately
provided to inject the fuel at a ratio set therebetween, the amount
of fuel injection can appropriately be corrected.
[0021] The foregoing and other objects, features, aspects and
advantages of the present invention will become more apparent from
the following detailed description of the present invention when
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a schematic configuration diagram of an engine
system controlled by a control device according to a first
embodiment of the present invention.
[0023] FIGS. 2 and 3 illustrate DI ratio maps in a warm state and a
cold state respectively, stored in an engine ECU serving as the
control device according to the first embodiment of the present
invention.
[0024] FIG. 4 is a first diagram showing a learning region of an
amount of fuel injection stored in the engine ECU serving as the
control device according to the first embodiment of the present
invention.
[0025] FIG. 5 is a second diagram showing a learning region of an
amount of fuel injection stored in the engine ECU serving as the
control device according to the first embodiment of the present
invention.
[0026] FIG. 6 is a flowchart showing a control configuration of a
program executed in the engine ECU serving as the control device
according to the first embodiment of the present invention.
[0027] FIG. 7 is a timing chart showing transition of the amount of
fuel injection.
[0028] FIG. 8 shows a state in which a learn value has been
calculated for each learning region, in each injection region.
[0029] FIGS. 9 and 10 illustrate DI ratio maps in a warm state and
a cold state respectively, stored in an engine ECU serving as a
control device according to a second embodiment of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] An embodiment of the present invention will be described
hereinafter with reference to the drawings. The same elements have
the same reference characters allotted. Their label and function
are also identical. Therefore, detailed description thereof will
not be repeated.
FIRST EMBODIMENT
[0031] FIG. 1 schematically shows a configuration of an engine
system controlled by an engine ECU (Electronic Control Unit) that
is a control device of an internal combustion engine according to a
first embodiment of the present invention. Although an in-line
4-cylinder gasoline engine is shown in FIG. 1, application of the
present invention is not restricted to the engine shown, and the
present invention is applicable to various types of engines such as
a V-type 6-cylinder engine, a V-type 8-cylinder engine and the
like.
[0032] As shown in FIG. 1, an engine 10 includes four cylinders
112, which are connected via corresponding intake manifolds 20 to a
common surge tank 30. Surge tank 30 is connected via an intake duct
40 to an air cleaner 50. In intake duct 40, an airflow meter 42 and
a throttle valve 70, which is driven by an electric motor 60, are
disposed. Throttle valve 70 has its opening position controlled
based on an output signal of an engine ECU 300, independently of an
accelerator pedal 100. Cylinders 112 are connected to a common
exhaust manifold 80, which is in turn connected to a three-way
catalytic converter 90.
[0033] For each cylinder 112, an in-cylinder injector 110 for
injecting fuel into the cylinder and an intake manifold injector
120 for injecting fuel into an intake port and/or an intake
manifold are provided. These injectors 110, 120 are controlled
based on output signals of engine ECU 300. In-cylinder injectors
110 are connected to a common fuel delivery pipe 130. Fuel delivery
pipe 130 is connected to a high-pressure fuel pump 150 of an engine
driven type via a check valve 140 that allows flow toward fuel
delivery pipe 130. In the present embodiment, description will be
made as to the internal combustion engine having two injectors
provided separately, although the present invention is not limited
thereto. For example, the internal combustion engine may have a
single injector capable of performing both in-cylinder injection
and intake manifold injection.
[0034] As shown in FIG. 1, the discharge side of high-pressure fuel
pump 150 is connected to the intake side of high-pressure fuel pump
150 via an electromagnetic spill valve 152. It is configured such
that the amount of the fuel supplied from high-pressure fuel pump
150 to fuel delivery pipe 130 increases as the degree of opening of
electromagnetic spill valve 152 is smaller, and that fuel supply
from high-pressure fuel pump 150 to fuel delivery pipe 130 is
stopped when electromagnetic spill valve 152 is fully opened.
Electromagnetic spill valve 152 is controlled based on an output
signal of engine ECU 300.
[0035] Meanwhile, intake manifold injectors 120 are connected to a
common fuel delivery pipe 160 on the low-pressure side. Fuel
delivery pipe 160 and high-pressure fuel pump 150 are connected to
a low-pressure fuel pump 180 of an electric motor driven type via a
common fuel pressure regulator 170. Further, low-pressure fuel pump
180 is connected to a fuel tank 200 via a fuel filter 190. Fuel
pressure regulator 170 is configured to return a part of the fuel
discharged from low-pressure fuel pump 180 to fuel tank 200 when
the pressure of the fuel discharged from low-pressure fuel pump 180
becomes higher than a preset fuel pressure. This prevents the
pressure of the fuel supplied to intake manifold injectors 120 as
well as the pressure of the fuel supplied to high-pressure fuel
pump 150 from becoming higher than the preset fuel pressure.
[0036] Engine ECU 300 is configured with a digital computer, which
includes a ROM (Read Only Memory) 320, a RAM (Random Access Memory)
330, a CPU (Central Processing Unit) 340, an input port 350, and an
output port 360, which are connected to each other via a
bidirectional bus 310.
[0037] Airflow meter 42 generates an output voltage that is
proportional to an intake air amount, and the output voltage of
airflow meter 42 is input via an A/D converter 370 to input port
350. A coolant temperature sensor 380 is attached to engine 10,
which generates an output voltage proportional to an engine coolant
temperature. The output voltage of coolant temperature sensor 380
is input via an A/D converter 390 to input port 350.
[0038] A fuel pressure sensor 400 is attached to fuel delivery pipe
130, which generates an output voltage proportional to a fuel
pressure in fuel delivery pipe 130. The output voltage of fuel
pressure sensor 400 is input via an A/D converter 410 to input port
350. An air-fuel ratio sensor 420 is attached to exhaust manifold
80 located upstream of three-way catalytic converter 90. Air-fuel
ratio sensor 420 generates an output voltage proportional to an
oxygen concentration in the exhaust gas, and the output voltage of
air-fuel ratio sensor 420 is input via an A/D converter 430 to
input port 350.
[0039] Air-fuel ratio sensor 420 in the engine system of the
present embodiment is a full-range air-fuel ratio sensor (linear
air-fuel ratio sensor) that generates an output voltage
proportional to an air-fuel ratio of the air-fuel mixture burned in
engine 10. As air-fuel ratio sensor 420, an O.sub.2 sensor may be
used which detects, in an on/off manner, whether the air-fuel ratio
of the mixture burned in engine 10 is rich or lean with respect to
a stoichiometric air-fuel ratio.
[0040] In the present embodiment, engine ECU 300 calculates a
feedback correction amount for the total fuel injection amount
based on the output voltage of air-fuel ratio sensor 420. In
addition, when a predetermined learning condition is satisfied,
engine ECU 300 calculates a learn value of the feedback correction
amount (a value representing constant deviation with regard to the
amount of fuel injection). Calculation of the feedback correction
amount and the learn value thereof are performed in a learning
region predetermined by using an intake air amount as a parameter.
The learning region will be described in detail later.
[0041] As to a method of calculating the feedback correction amount
and the learn value thereof, a technique commonly used in the
internal combustion engine including one injector for each cylinder
is used. Therefore, detailed description thereof will not be
repeated.
[0042] Accelerator pedal 100 is connected to an accelerator
position sensor 440 that generates an output voltage proportional
to a degree of press-down of accelerator pedal 100. The output
voltage of accelerator position sensor 440 is input via an A/D
converter 450 to input port 350. An engine speed sensor 460
generating an output pulse representing the engine speed is
connected to input port 350. ROM 320 of engine ECU 300 prestores,
in the form of a map, values of fuel injection amount that are set
corresponding to operation states based on the engine load factor
and the engine speed obtained by the above-described accelerator
position sensor 440 and engine speed sensor 460, respectively, and
the correction values based on the engine coolant temperature.
[0043] Referring to FIGS. 2 and 3, maps each indicating a fuel
injection ratio between in-cylinder injector 110 and intake
manifold injector 120 (hereinafter, also referred to as a DI ratio
(r)), identified as information associated with an operation state
of engine 10, will now be described. The maps are stored in ROM 320
of engine ECU 300. FIG. 2 is the map for a warm state of engine 10,
and FIG. 3 is the map for a cold state of engine 10.
[0044] In the maps illustrated in FIGS. 2 and 3, with the
horizontal axis representing an engine speed of engine 10 and the
vertical axis representing a load factor, the fuel injection ratio
of in-cylinder injector 110, or the DI ratio r, is expressed in
percentage.
[0045] As shown in FIGS. 2 and 3, the DI ratio r is set for each
operation region that is determined by the engine speed and the
load factor of engine 10. "DI RATIO r=100%" represents the region
where fuel injection is carried out using only in-cylinder injector
110, and "DI RATIO r=0%" represents the region where fuel injection
is carried out using only intake manifold injector 120. "DI RATIO
r.noteq.0%", "DI RATIO r.noteq.100%" and "0%<DI RATIO r<100%"
each represent the region where fuel injection is carried out using
both in-cylinder injector 110 and intake manifold injector 120.
Generally, in-cylinder injector 110 contributes to an increase of
output performance, while intake manifold injector 120 contributes
to uniformity of the air-fuel mixture. These two kinds of injectors
having different characteristics are appropriately selected
depending on the engine speed and the load factor of engine 10, so
that only homogeneous combustion is conducted in the normal
operation state of engine 10 (other than the abnormal operation
state such as a catalyst warm-up state during idling).
[0046] Further, as shown in FIGS. 2 and 3, the fuel injection ratio
between in-cylinder injector 110 and intake manifold injector 120,
or the DI ratio r, is defined individually in the map for the warm
state and in the map for the cold state of the engine. The maps are
configured to indicate different control regions of in-cylinder
injector 110 and intake manifold injector 120 as the temperature of
engine 10 changes. When the temperature of engine 10 detected is
equal to or higher than a predetermined temperature threshold
value, the map for the warm state shown in FIG. 2 is selected;
otherwise, the map for the cold state shown in FIG. 3 is selected.
One or both of in-cylinder injector 110 and intake manifold
injector 120 are controlled based on the selected map and according
to the engine speed and the load factor of engine 10.
[0047] In the present embodiment, the amount of fuel injection from
in-cylinder injector 110 and the amount of fuel injection from
intake manifold injector 120 are determined based on DI ratio r
such that the total fuel injection amount attains the desired
injection amount.
[0048] The engine speed and the load factor of engine 10 set in
FIGS. 2 and 3 will now be described. In FIG. 2, NE(1) is set to
2500 rpm to 2700 rpm, KL(1) is set to 30% to 50%, and KL(2) is set
to 60% to 90%. In FIG. 3, NE(3) is set to 2900 rpm to 3100 rpm.
That is, NE(1)<NE(3). NE(2) in FIG. 2 as well as KL(3) and KL(4)
in FIG. 3 are also set as appropriate.
[0049] When comparing FIG. 2 and FIG. 3, NE(3) of the map for the
cold state shown in FIG. 3 is greater than NE(1) of the map for the
warm state shown in FIG. 2. This shows that, as the temperature of
engine 10 is lower, the control region of intake manifold injector
120 is expanded to include the region of higher engine speed. That
is, in the case where engine 10 is cold, deposits are unlikely to
accumulate in the injection hole of in-cylinder injector 110 (even
if the fuel is not injected from in-cylinder injector 110). Thus,
the region where the fuel injection is to be carried out using
intake manifold injector 120 can be expanded, to thereby improve
homogeneity.
[0050] When comparing FIG. 2 and FIG. 3, "DI RATIO r=100%" in the
region where the engine speed of engine 10 is NE(1) or higher in
the map for the warm state, and in the region where the engine
speed is NE(3) or higher in the map for the cold state. In terms of
load factor, "DI RATIO r=100%" in the region where the load factor
is KL(2) or greater in the map for the warm state, and in the
region where the load factor is KL(4) or greater in the map for the
cold state. This means that in-cylinder injector 110 solely is used
in the region of a predetermined high engine speed, and in the
region of a predetermined high engine load. That is, in the high
speed region or the high load region, even if fuel injection is
carried out using only in-cylinder injector 110, the engine speed
and the load of engine 10 are high, ensuring a sufficient intake
air amount, so that it is readily possible to obtain a homogeneous
air-fuel mixture even using only in-cylinder injector 110. In this
manner, the fuel injected from in-cylinder injector 110 is atomized
within the combustion chamber involving latent heat of vaporization
(or, absorbing heat from the combustion chamber). Thus, the
temperature of the air-fuel mixture is decreased at the compression
end, whereby antiknock performance is improved. Further, since the
temperature within the combustion chamber is decreased, intake
efficiency improves, leading to high power output.
[0051] In the map for the warm state in FIG. 2, fuel injection is
carried out using only in-cylinder injector 110 when the load
factor is KL(1) or less. This shows that in-cylinder injector 110
alone is used in a predetermined low load region when the
temperature of engine 10 is high. When engine 10 is in the warm
state, deposits are likely to accumulate in the injection hole of
in-cylinder injector 110. However, when fuel injection is carried
out using in-cylinder injector 110, the temperature of the
injection hole can be lowered, whereby accumulation of deposits is
prevented. Further, clogging of in-cylinder injector 110 may be
prevented while ensuring the minimum fuel injection amount thereof
Thus, in-cylinder injector 110 alone is used in the relevant
region.
[0052] When comparing FIG. 2 and FIG. 3, there is a region of "DI
RATIO r=0%" only in the map for the cold state in FIG. 3. This
shows that fuel injection is carried out using only intake manifold
injector 120 in a predetermined low load region (KL(3) or less)
when the temperature of engine 10 is low. When engine 10 is cold
and low in load and the intake air amount is small, atomization of
the fuel is unlikely to occur. In such a region, it is difficult to
ensure favorable combustion with the fuel injection from
in-cylinder injector 110. Further, particularly in the low-load and
low-speed region, high output using in-cylinder injector 110 is
unnecessary. Accordingly, fuel injection is carried out using only
intake manifold injector 120, rather than in-cylinder injector 10,
in the relevant region.
[0053] Further, in an operation other than the normal operation, or
in the catalyst warm-up state during idling of engine 10 (abnormal
operation state), in-cylinder injector 110 is controlled to carry
out stratified charge combustion. By causing the stratified charge
combustion only during the catalyst warm-up operation, warming up
of the catalyst is promoted, and exhaust emission is thus
improved.
[0054] Moreover, in the present embodiment, aside from the map for
the cold state shown in FIG. 3, DI ratio r is set to 0% (DI ratio
r=0%), that is, the fuel is injected solely from intake manifold
injector 120, at the time of cold start of engine 10 (at the time
of start when the temperature of the coolant in the internal
combustion engine is lower than the predetermined temperature).
Therefore, during cranking when the temperature of the coolant in
the internal combustion engine is lower than the predetermined
temperature, the fuel is injected solely from intake manifold
injector 120. In addition, during idling when engine 10 is cold
(during idling when the temperature of the coolant of the internal
combustion engine is lower than the predetermined temperature), the
fuel is injected solely from intake manifold injector 120. It is
noted that the fuel may be injected solely from in-cylinder
injector 10, instead of intake manifold injector 120.
[0055] A learning region where a feedback correction amount and a
learn value thereof are calculated will now be described with
reference to FIGS. 4 and 5. FIG. 4 shows a learning region in the
map for the warm state, while FIG. 5 shows a learning region in the
map for the cold state.
[0056] In FIGS. 4 and 5, regions adjacent to each other delimited
by chain dotted curves represent the learning regions. The learning
region is divided in accordance with an intake air amount. The
learning region is set in accordance with the intake air amount
because error in output of airflow meter 42 is different depending
on the intake air amount.
[0057] In the present embodiment, four learning regions, i.e.,
learning regions (1) to (4), are provided. The intake air amount is
largest in learning region (1), second largest in learning region
(2), then learning region (3), and smallest in learning region (4).
It is noted that the number of learning regions is not limited to
four.
[0058] In the present embodiment, the feedback correction amount
and the learn value thereof are calculated not only for each
learning region but also for each injection region (a region where
DI ratio r=100%, a region where 0%<DI ratio r<100%, and a
region where DI ratio r=0%). In other words, the feedback
correction amount and the learn value thereof are calculated for
each learning region in each injection region.
[0059] A control configuration of a program executed in engine ECU
300 serving as the control device for the internal combustion
engine according to the present embodiment will be described with
reference to FIG. 6.
[0060] At step (hereinafter, step is abbreviated as S) 100, engine
ECU 300 determines whether or not a request for starting engine 10
has been detected. For example, when an operation to turn on a
start switch has been performed or when an ignition key has been
turned to a start position, it is determined that the request for
starting engine 10 has been detected. When the request for start
has been detected (YES at S100), the process proceeds to S102.
Otherwise (NO at S100), the process returns to S100. At S102,
engine ECU 300 starts engine 10 by transiently increasing the
amount of fuel injection and by cranking engine 10.
[0061] At S104, engine ECU 300 detects a coolant temperature TW of
engine 10 based on a signal transmitted from coolant temperature
sensor 380. At S106, engine ECU 300 determines whether or not
coolant temperature TW is lower than a threshold value TW(0). When
coolant temperature TW is lower than threshold value TW(0) (YES at
S106), the process proceeds to S108. Otherwise (NO at S106), the
process ends.
[0062] At S108, engine ECU 300 determines whether or not a
condition for stopping transient increase in the amount of fuel
injection is satisfied. Here, the condition for stopping transient
increase refers to such a condition that engine 10 attains full
combustion (the engine speed of engine 10 is higher than a
predetermined engine speed). It is noted that the condition for
stopping transient increase is not limited as such.
[0063] When the condition for stopping transient increase is
satisfied (YES at S108), the process proceeds to S110. Otherwise
(NO at S108), the process proceeds to S112. At S110, engine ECU 300
stops transient increase in the amount of fuel injection. At S112,
engine ECU 300 prohibits calculation (update) of the learn
value.
[0064] At S114, engine ECU 300 steadily increases the amount of
fuel injection in accordance with coolant temperature TW. For
example, as coolant temperature TW is lower, the amount of fuel
injection is increased. At S116, engine ECU 300 permits calculation
(update) of the learn value.
[0065] At S118, engine ECU 300 determines whether or not a
condition for stopping steady increase in the amount of fuel
injection is satisfied. Here, the condition for stopping steady
increase refers to such a condition that the temperature of engine
10, that is, coolant temperature TW, is higher than the
predetermined temperature. It is noted that the condition for
stopping steady increase is not limited as such, and the condition
may be such that a predetermined time period has elapsed since stop
of transient increase or the accumulated engine speed after the
stop of transient increase exceeds a predetermined engine speed.
When the condition for stopping steady increase is satisfied (YES
at S118), the process proceeds to S120. Otherwise (NO at S118), the
process returns to S118.
[0066] At S120, engine ECU 300 stops steady increase in the amount
of fuel injection. Thereafter, the process ends.
[0067] An operation of engine ECU 300 serving as the control device
for the internal combustion engine according to the present
embodiment based on the configuration and the flowchart above will
now be described.
[0068] When the request for start is detected from a non-operating
state of engine 10 (YES at S100), in order to improve starting
capability, the amount of fuel injection is transiently increased
and cranking of engine 10 is started as shown in FIG. 7, whereby
engine 10 is started (S102).
[0069] During this state, the air-fuel ratio is unstable and may
suddenly change. Therefore, if a learn value is calculated during
transient increase, miscalculation of the learn value and hence
unnecessary correction of the amount of fuel injection is
likely.
[0070] As there is an occasion to calculate a learn value in the
region where DI ratio r=100% and in the region where 0%<DI ratio
r<100% after warm-up of engine 10, influence by erroneous
learning is slight. On the other hand, as it is solely during the
cold state that a learn value in the region where DI ratio r=0% is
calculated, the learn value should be calculated with higher
accuracy.
[0071] Therefore, when the engine is started, coolant temperature
TW is detected (S104) and whether or not coolant temperature TW is
lower than threshold value TW(0) is determined (S106). If coolant
temperature TW is lower than threshold value TW(0) (YES at S106),
that is, during the cold state of engine 10, whether or not the
condition for stopping transient increase in the amount of fuel
injection has been satisfied is determined (S108).
[0072] If the condition for stopping transient increase in the
amount of fuel injection has not been satisfied (NO at S108), that
is, if transient increase in the amount of fuel injection
continues, calculation of the learn value is prohibited (S112).
Unnecessary correction of the amount of fuel injection caused by
calculation of the learn value in such a state that the air-fuel
ratio may suddenly change can thus be suppressed.
[0073] On the other hand, when the condition for stopping transient
increase in the amount of fuel injection has been satisfied (YES at
S108), that is, when engine 10 attains full combustion, transient
increase in the amount of fuel injection is stopped (S110). Here,
it is assumed as shown in FIG. 7 that, after engine 10 attains full
combustion at time T(1), the amount of fuel injection is gradually
decreased and transient increase in the amount of fuel injection is
stopped at time T(2).
[0074] Even after transient increase is stopped, it is difficult to
atomize the fuel during the cold state, and the engine speed of
engine 10 may not be maintained at the desired engine speed with a
normal amount of fuel injection (the same as the amount of fuel
injection during the warm state). Therefore, the amount of fuel
injection is steadily increased in accordance with coolant
temperature TW (S114). The operation state of engine 10 during this
period includes idling.
[0075] When the amount of fuel injection is steadily increased, it
can be said that the air-fuel ratio is stable. Therefore, when a
learn value is calculated during this period, miscalculation is
less likely. Meanwhile, an occasion to calculate the learn value in
the region where DI ratio r=0%, that is, the learn value when the
fuel is injected solely from intake manifold injector 120, is
limited to those during the cold state. Therefore, it is necessary
to ensure as many occasions as possible to calculate the learn
value also during the cold state, as well as to accurately
calculate the learn value in the region where DI ratio r=0%.
[0076] Therefore, while the amount of fuel injection is steadily
increased in accordance with coolant temperature TW, calculation of
the learn value is permitted (S116). Thus, the learn value is
calculated while the air-fuel ratio is stable, and the learn value
can be obtained for each learning region in each injection region
(particularly in the region where DI ratio r=0%), as shown in FIG.
8. Though not shown, the learn value when DI ratio r=0% during
idling can be obtained.
[0077] FIG. 8 shows a state in which one learn value has been
calculated for each learning region in each injection region. In
FIG. 8, squares indicate learn values in the region where DI ratio
r=100%, circles indicate learn values in the region where 0%<DI
ratio r<100%, and triangles indicate learn values in the region
where DI ratio r=0%.
[0078] Thereafter, when the condition for stopping steady increase
in the amount of fuel injection is satisfied (YES at S118), that
is, when the condition that coolant temperature TW is higher than
the predetermined temperature is satisfied, steady increase in the
amount of fuel injection is stopped (S120).
[0079] As described above, according to the engine ECU serving as
the control device for the internal combustion engine according to
the present embodiment, while the engine is in the cold state and
when the amount of fuel injection is transiently increased at the
time of start of engine, calculation of the learn value is
prohibited. While the amount of fuel injection is steadily
increased in accordance with coolant temperature TW after transient
increase is stopped, calculation of the learn value is permitted.
In this manner, erroneous learning of the learn value while the
air-fuel ratio may suddenly change can be suppressed and the learn
value can accurately be calculated. Therefore, unnecessary
correction of the amount of fuel injection can be suppressed.
Consequently, the air-fuel ratio can be controlled to be
appropriate and exhaust emission performance can be improved.
[0080] When the amount of fuel injection is transiently corrected,
for example, based on the fuel adhered to the wall surface of the
intake port or the fuel purged from the canister (not shown), the
air-fuel ratio becomes unstable. Accordingly, the learn value
calculated during such correction while the amount of fuel
injection is steadily increased in accordance with coolant
temperature TW may not be stored in RAM 330 so as to prohibit
correction of the amount of fuel injection based on that learn
value.
SECOND EMBODIMENT
[0081] Referring to FIGS. 9 and 10, a second embodiment of the
present invention will be described. In the present embodiment, DI
ratio r is calculated using a map different from those in the first
embodiment described previously.
[0082] As the configuration and the process flow as well as
functions thereof are otherwise the same as those in the first
embodiment described previously, detailed description thereof will
not be repeated.
[0083] Referring to FIGS. 9 and 10, maps each indicating the fuel
injection ratio between in-cylinder injector 110 and intake
manifold injector 120, identified as information associated with
the operation state of engine 10, will be described. The maps are
stored in ROM 320 of engine ECU 300. FIG. 9 is the map for the warm
state of engine 10, and FIG. 10 is the map for the cold state of
engine 10.
[0084] FIGS. 9 and 10 differ from FIGS. 2 and 3 in the following
points. "DI RATIO r=100%" holds in the region where the engine
speed of engine 10 is equal to or higher than NE(1) in the map for
the warm state, and in the region where engine 10 speed is NE(3) or
higher in the map for the cold state. Further, except for the
low-speed region, "DI RATIO r=100%" holds in the region where the
load factor is KL(2) or greater in the map for the warm state, and
in the region where the load factor is KL(4) or greater in the map
for the cold state. This means that fuel injection is carried out
using only in-cylinder injector 110 in the region where the engine
speed is at a predetermined high level, and that fuel injection is
often carried out using only in-cylinder injector 110 in the region
where the engine load is at a predetermined high level. However, in
the low-speed and high-load region, mixing of an air-fuel mixture
formed by the fuel injected from in-cylinder injector 110 is poor,
and such inhomogeneous air-fuel mixture within the combustion
chamber may lead to unstable combustion. Thus, the fuel injection
ratio of the in-cylinder injector is increased as the engine speed
increases where such a problem is unlikely to occur, whereas the
fuel injection ratio of in-cylinder injector 110 is decreased as
the engine load increases where such a problem is likely to occur.
These changes in the DI ratio r are shown by crisscross arrows in
FIGS. 9 and 10. In this manner, variation in output torque of the
engine attributable to the unstable combustion can be suppressed.
It is noted that these measures are approximately equivalent to the
measures to decrease the fuel injection ratio of in-cylinder
injector 110 as the state of engine 10 moves toward the
predetermined low speed region, or to increase the fuel injection
ratio of in-cylinder injector 10 as engine 10 state moves toward
the predetermined low load region. Further, except for the relevant
region (indicated by the crisscross arrows in FIGS. 9 and 10), in
the region where fuel injection is carried out using only
in-cylinder injector 10 (on the high speed side and on the low load
side), a homogeneous air-fuel mixture is readily obtained even when
the fuel injection is carried out using only in-cylinder injector
110. In this case, the fuel injected from in-cylinder injector 110
is atomized within the combustion chamber involving latent heat of
vaporization (by absorbing heat from the combustion chamber).
Accordingly, the temperature of the air-fuel mixture is decreased
at the compression end, and thus, the antiknock performance
improves. Further, with the temperature of the combustion chamber
decreased, intake efficiency improves, leading to high power
output.
[0085] In engine 10 explained in the first and second embodiments,
homogeneous combustion is achieved by setting the fuel injection
timing of in-cylinder injector 10 in the intake stroke, while
stratified charge combustion is realized by setting it in the
compression stroke. That is, when the fuel injection timing of
in-cylinder injector 110 is set in the compression stroke, a rich
air-fuel mixture can be located locally around the spark plug, so
that a lean air-fuel mixture in the combustion chamber as a whole
is ignited to realize the stratified charge combustion. Even if the
fuel injection timing of in-cylinder injector 110 is set in the
intake stroke, stratified charge combustion can be realized if it
is possible to provide a rich air-fuel mixture locally around the
spark plug.
[0086] As used herein, the stratified charge combustion includes
both the stratified charge combustion and semi-stratified charge
combustion. In the semi-stratified charge combustion, intake
manifold injector 120 injects fuel in the intake stroke to generate
a lean and homogeneous air-fuel mixture in the whole combustion
chamber, and then in-cylinder injector 10 injects fuel in the
compression stroke to generate a rich air-fuel mixture around the
spark plug, so as to improve the combustion state. Such
semi-stratified charge combustion is preferable in the catalyst
warm-up operation for the following reasons. In the catalyst
warm-up operation, it is necessary to considerably retard the
ignition timing and maintain a favorable combustion state (idle
state) so as to cause a high-temperature combustion gas to reach
the catalyst. Further, a certain amount of fuel needs to be
supplied. If the stratified charge combustion is employed to
satisfy these requirements, the amount of the fuel will be
insufficient. If the homogeneous combustion is employed, the
retarded amount for the purpose of maintaining favorable combustion
is small compared to the case of stratified charge combustion. For
these reasons, the above-described semi-stratified charge
combustion is preferably employed in the catalyst warm-up
operation, although either of stratified charge combustion and
semi-stratified charge combustion may be employed.
[0087] Further, in the engine explained in the first and second
embodiments, the fuel injection timing of in-cylinder injector 110
is preferably set in the intake stroke in a basic region
corresponding to the almost entire region (here, the basic region
refers to the region other than the region where semi-stratified
charge combustion is carried out with fuel injection from intake
manifold injector 120 in the intake stroke and fuel injection from
in-cylinder injector 110 in the compression stroke, which is
carried out only in the catalyst warm-up state). The fuel injection
timing of in-cylinder injector 110, however, may be set temporarily
in the compression stroke for the purpose of stabilizing
combustion, for the following reasons.
[0088] When the fuel injection timing of in-cylinder injector 110
is set in the compression stroke, the air-fuel mixture is cooled by
the injected fuel while the temperature in the cylinder is
relatively high. This improves the cooling effect and, hence, the
antiknock performance. Further, when the fuel injection timing of
in-cylinder injector 110 is set in the compression stroke, the time
from the fuel injection to the ignition is short, which ensures
strong penetration of the sprayed fuel, so that the combustion rate
increases. The improvement in antiknock performance and the
increase in combustion rate can prevent variation in combustion,
and thus, combustion stability is improved.
[0089] Regardless of the temperature of engine 10 (that is, whether
engine 10 is in the warm state or in the cold state), the warm
state map shown in FIG. 2 or 9 may be used during idle-off state
(when an idle switch is off, or when the accelerator pedal is
pressed) (regardless of whether engine 10 is in the cold state or
in the warm state, in the low load region, in-cylinder injector 110
is used).
[0090] Although the present invention has been described and
illustrated in detail, it is clearly understood that the same is by
way of illustration and example only and is not to be taken by way
of limitation, the spirit and scope of the present invention being
limited only by the terms of the appended claims.
* * * * *